314 Mr. Harvey's experimental inquiries relative to the 
bar, was determined in the centre of a meadow, and of which 
the substratum was clay slate,* by a mean of six sets of ex- 
periments, performed with the utmost care ; the time being 
registered to quarter seconds. The instrument was then 
taken on board, and placed in succession at the different sta- 
tions previously assumed in the ship, and the mean of six 
sets of experiments determined at each station, with the 
same care as on land. The times of performing the oscilla- 
tions on shore, and at each of the assumed points in the ship, 
necessarily gave the magnetic intensity at each station in 
terms of the terrestrial intensity, and which, in this case, was 
represented by 100. 
The succeeding table contains the results of the mean in- 
tensities of the stations assumed on the poop, forecastle, the 
upper and lower decks of the vessel, for the positions in 
which she was successively moored. 
* It is of importance in magnetic inquiries, to attend to the circumstances of the 
place in which the experiments are performed. With a delicate apparatus, like 
that here alluded to, the proximity of houses has a sensible effect. Even in differ- 
ent rooms of the same house a change of intensity has been observed, when no 
other iron has been near the instrument than what might have existed in the par- 
titions and floors. When the intensity as determined in one house was denoted by 
ioo, the same needle in another house, two hours after, gave only a result of 93.2. 
This was determined more than once. Each house was built on clay slate. 
